Respuesta :

Renae360

Answer:

The average speed per hour of Shelly is 5.25 minutes.

Step-by-step explanation:

We can do proportion to solve this.

[tex] \frac{21 \: miles}{4 \: hours} = \frac{x}{1 \: hour} \\ \frac{4x}{4} = \frac{21}{4} \\ x = 5.25[/tex]